Shock absorber



Patented Jan. 8, 1929.

UNITED STATES RALPH M. LOVEJ' OY, BOSTON, MASSACHUSETTS.

SHOCK ABSORBER.

Application el'd November 22, 1926. Serial No. 149,859.

This invention relates to improvements in hydraulic shock absorbers andthe general object thereof is to provide an instrument which willoperate more effectively to absorb both light and heavy shocks. Theinvention relates more particularly to the type of hydraulic shockabsorber which is disclosed in 4my prior Patent No. 1,324,913 grantedI.)e cember 16, 1919, which comprises a casnig having a reservoir and acylinder provided with a valved inlet communicating with said reservoiradapted to permit a substantially .free flow of liquid from thereservoir into the cylinder and to prevent the flow of the liquid fromthe cylinder to thereservon, a piston reciprocabl'e in said cylinder anda relief port having a spring actuated valve adapted to permit arestricted flow of liquldy from the cylinder to the reservoir 1nresponse to compressive movements of the piston.

It has been found in the operation of such shock absorbers that if thespring for the relief valve is of sufficient strength properly torestrict the flow of liquid fromthe cylinder in response to heavy shockswhich cause an extended and rapid movement'of the piston it will notyield suiiieiently to absorb prop- X erly slight shocks such as arecaused when a vehicle, equipped with such shock absorbers, is passingover a cobbled pavement, or a slightly rough road surface. On the otherhand, if the relief valve spring is sufficiently light to be properlyresponsive to relatively slight movements of the piston it will notoffer sufficient resistance to the full and rapid y movements of thepiston caused by major shocks.

The object, therefore, of the present'linvention is to provide reliefvalve mechanlsm of greater flexibility whichwill respond properly toslight movements of the piston and will also afford proper resistance tothe .pressure in the cylinder caused by the greater movements thereof.

More particularly the object 'of the'invention is to provide the reliefport with a compound relief valveconstruction comprising a main valvefor resisting the flow of liquid caused by the greater movements of thepiston and an auxiliary valve responsive to rela- .tivelyslightm'ovements ofthe piston,

A further object of the invention is to provide a compound relief valveof the Icharacter speciiied with a port of restricted area'adaptl ed toimpose a resistance to the flovv'of liquid upon the )relatively slightmovements of the' piston with a co-ope rating valve under the influenceof a relatively light spring.

A further object of the invention is to provide means for preventing theclogging of the relatively small auxiliary valve port.

A further object of the invention is to provide a simplified shockabsorber construction in which the relief port is located substantiallymidway of the length of the cylinder thus producing a more economicalshock absorber construction by the saving of4 considerable metal andalso providing a smaller, but suflicient reservoir for the liquid.

Other objects and features of the invention will more fully appear fromthe following description and the accompanying drawings and will beparticuarly pointed out in the claims.l

In the drawings:

Fig. 1 is a vertical longitudinal sectional View of a shock absorberembodying the invention;

Fig. 2 isa transverse sectional view on line 2 2 Fig. 1 lookingdownward;

Fig. 3 is a perspective View of the tubular piston illustrating the slottherein which communicates with the relief ort;

AFig. 4 is an enlarged vertica sectional view of the compound reliefvalve and illustrating the manner in which the same is mounted in therelief port and casing;

Fig. 5 is a fragmentary view, mainly in longitudinal vertical section,through the cylinder and the tubular piston; and,

Fig. 6.is a detail View of the screen or filter for preventing theclogging of the restrictedv portin the relief valve.

' 'The shock absorber illustratedin Fig. lcomprises a casingvl havinganlinterior cylindrical wall 2 dividing the chamber of the casing desirably is provided with ears 5 and 6 having apertures to receive bolts bymeans of which the. casing may b e secured to one of two relativelymovable members, such as the frame of a vehicle. f The casing isprovided with a cover 7 having laterallyextcnding ears 8 which aresecured by suitable machine screws 9 to the into a reservoir 3 and acylinder4. Thecasing 'V i ing, preferably rectangular, boss 13 having@transverse bearing therethrough-'toreceive a pintle or shaft 14 which isconnected by links 15 to a similar pintle or shaft 16 in the end portionof an arm 17 which is rigidly secured to a rock shaft 18 by a pin 19which enters said rock yshaft and is provided with a screw threadedvsection 20 which engages complementary walls in said arm. The rockshaftv skilled in the art.

The under face of the iston head 11 is provided with alcountersin orlrecess 21 and is also provided ,withv apertures 22 which desirablyextend obliquely upwardly from said recess and'communicate with theupper prtion ofthe cylinder which is in communication with thereservoir, thus providing an inlet from the reservoir to the cylinderbeneath the iston head.

T inlet to the cylinder is provided with a suitable valve adapted` topermit a substan-` tially free flow of the liquid from the reservoirinto the cylinder, but to prevent flow of the liquid in the reversedirection. In the 'preferred form illustrated herein the-valve mechanismcomprises an annular valve cage, provid ed with a peripheral flange 24which rests upon a -suitable seat on the lower face of thedpiston head.The'valve" cage is held in seated position by a helical spring 25 whichis interposed between the flange 24 of the valve cage and the head 26 ofthe cylinder. The valve cage desirably is in the form of a spider 27having a4 central stud 28 secured .thereto upon which a valve 29 isslidably mounted and retained normally in engagement therewithv by alightfhelical spring 30 the upper end of which engage the valve 29 andthe lower end of which rests .upon a lpin 31 extending through the valvestem 28. Desirably the valve`29'presents a flat face and the valve cage23 is provided with an annular valve seat in the form of a Isharpedge 32formed by bevel--y Ivling the wallsy 'of the valve seat, therebyproducing a' substantially line engagement with the fiatsurface ofy thevalve which will avoid the likelihood of sticking, thusinsuring thefreedom `of movement of the valve during the intake stroke ofthe pistonand permitting a substantially free flow "ofthe liquid from thereservoirltherethrough into the cylinder..

The inner jwall 2 of the casing, which di# vides the reservoir from thecylinder, desir-2,1 y

relief,v ortunder all conditions of reciproca- 'ably is provided with athickened portion 33 having therein a cylindrical relief port 34 whichis controlled by a spring actuated rei t lief valve. This relief portdesir-ably is loscated approximately midway of the length of `prising a.main valve having 'a springjof the cylinder and maybe positionedclosely adjacent to the bottom of the reservoir. By virtue of thisarrangement a much smaller reservoir for the excess'of liquid requiredmay be iemployed and considerable saving made in the amount of materialrequired to form the shock absorber casing.

' `The cylindrical skirt of the piston is provided with an aperture 35which communicates with the relief port 34 and desirably is of suchlength as to maintain constant .Com-

munication with said port Iduring the full. re-

ciprocation of the piston. This aperture may be in the form of aslot,1a`s illustrated in Fig'. 3, or may bea series 'of apertures insuch proximity. as to`permit a substantially continuous flow'of theliquid fromthe cylinder through the port when sufficient pressure isimpose upon the` liquid in the cylinder to unseat the relief valve orvalves. The shock absorber so far described is simi ilar in principle tothe commercial shock absorbers of the type above described. In theoperation of shock absorbers of. this type as applied to an automobile,.or other vehicle, the compression of the spring'sof the vehicle,resulting from obstructions l. or depressions ofthe surface of the road,reduces the tension vupon the outer arm of the shockabsorber,

thus permitting the helical spring 25 to raise the piston within thecylinder. As the pis" ton is thus raised li uid Hows from the reservoirthrough the in et port 22, unseating the valve -29 and entering thecylinder beneath the valve.y Upon rebounding movement of* the spring`theoutside arm is in ovedin the opposite irection, forcing downwardlythe inside arm 17, and the piston, thus exerting a compressive forceupon the 1i uid which is in the cylinder. As the inlet va ve 29 is thenclosed such resistance to the descent of the,` piston is offered asiscontrolled by the resistance of the relief valve tothe flow of theliquid through theport 34. In previousconstructions the amount of'resistance to 'the descent of the piston has been determined by thestrengthl of the spriiig of the relief valve and, as heretofore stated,it has been practicallyl impossible to` provide a spring of suchstrength as will effectively resist the pressure of the liquid *duringlong and rapid movements of the piston, and also provide a suiiicientlyless resistance to permit the instrument to respond-properly to shockswhich produce relatively short movements o f the piston. y H

The principal object of the invention,

v therefore, is to provide a compound valve v(instruction `which willproduce the required resistaii'ce to lthe flow of liquid through the 125tion' o the'pi'ston. This'f'is accomplished by providing a compoundvalve mechanism com-I` sulicient strength to cause the valve to offerLee-82640 are obtained when the vehicle is passing over a cobbledsurface or the like.

The preferred construction of the relief valve is illustrated in Fig. 1and Ain enlarged detail in Fig. 4. This valve construction comprises atubular valve having a head 36 Which engages an annular valve seat 37 inthe enlarged portion 33 of the Wall 2 and a cylindrical portion 38slidably fitting the i Walls of the relief port 34. The cylindricalportion of the tubular valve is provided with one or more apertures 39through which liquid may flow from the relief port to the reservoir whenthe valve fis forced from its seat. The head of the valve is providedwith a desirably conoidal inner face 40 converg` ing -to a cenyral port41 which communicates with a tubu ar valve stem 42 Which desirably isintegral with the head 36 of the valve. .The valve' port 42 is ofrelatively small area and, therefore, permits a restricted flow ofliquid therethrough. Desirably a screen 43 is located Within thecylindrical section of the tubular valve and serves to prevent foreignmaterial from clogging the restricted valve port 41. This screendesirably is of sheet metal comprising a sheet, having very smallperforations, stamped into convex form and after insertion at the baseof the cylindrical section of the tubular valve'expanded int`o asuitable annular recess therein.

The stem 42 of the valve is of cylindrical form and is provided at-itsouter end with a closure presenting a restricted opening. i The end ofthe tubular valve stem adjacent the cylinder desirably isprovided with aconidal wall 44 which may conform to the end of a drill employed to borethe chamber in the valve stem, this Wall formin the seat for anauxiliary valve. The pre erred form of auxiliary valve illustratedherein comprises a cylindrical plunger 45 which slidably fits in thetubular valve stem and has a solid imor chamber 47 and an aperture 48 isprovided f in the reduced Wallcommunicating with the chamber of thevalve. The valve is held normally in seated position by a helical spring49 Which abuts at one end against the outer end of the hollow valve andat its other end vagainst a suitable abutment which is rigidly securedinthe. valve stem. Preferably the outer end of the valve stem isprovided with a restricted outlet for the liquid which is forced throughthe valve stem. A convenient construction, which is illustrated herein,comprises a plug or'collar 50, having a central restricted aperture 51oif suitable diameter, which is secured in the outer end of the valvestem by the svvaged or spun-over end portion 52 of the valve stem.

The valve stem desirably extends into a cylindrical chamber 53 in a plug54, having a screw threaded stem 55 which enters and engages the screwthreaded wall of an aperl ture in a boss 56 of the casing. The chamber53 1s of slightly larger diameter than the diameter of the valve stem sothat the liquid,

vwhich is forced into the chamber, will build up a pressure upon the endof the valve steln Whichiis complementary to the pressure imposed by thepiston upon the liquid in the cylinderduring its compressive niovement.A helical spring 57, surrounding the valve stem 42 and abutting at oneend against the inner end of the plug 52 and at its other end againstthe head 36 of the main valve, serves to urge the main valve towardvSeated position. n l

By reason of this construction the auxiliary valve is yieldable to thepressure imposed by the piston upon the liq i'd in the cylinder causedby slight shockswhile the restricted area of the auxiliary alve port 40is too small to permit a suliiciently rapid descent ofthe piston. finresponse to thev heavier shocks, so that sufficient pressure will bebuilt up Within the cylinder to unseat the by the valve suiiiciently tocheck graduallyl the descent of the piston and thus absorb a majorshock.

The flow of the liquid through the auxiliary valve port 41 firstdisplaces the auxiliary valve from its seat and then flows through thechamber 47 and aperture 48 into the chamber of the valve 45 and fromthis chamber through the restricted aperture 51 into the chamber 53 inthe plug. Inasmuch as the valve stem is provided with but littleclearance from the Wall of the chamber in the plug, pressure isyaccumulated in the. chamber' 53, when the pressure in the cylinder isgreat-ly increased, which acts upon the end of the valve stem andthereby tends to force the valve toward its seat in addition to theforce of the main valve spring 57. Thus the resistance of the main valveto displacement is correlated in ameasure to the pressure imposed by thepiston upon the liquid in the y cylinder when thepiston is `givenrelatively great and rapid movements which impose a heavy pressure uponthe liquid in theeylv inder. On the other hand relatively slightmovements of the piston are resisted mainly or Wholly by the restricted'1 v`alve port y'41 and the` spring actuated auxiliary valveizf -and such`further resistance as'may be -1A upon the liquid' byf'the restrictedpassage 51 in the outer end of the valve stem and thev sed I y ladpassage between the outer surface of the valve, a light springa actingnormally to seat valve stem and the Wall of the chamber in saidauxiliary valve and a relativelyV heavy ance to the movement of thepiston isvob` oil therefrom directly into the reservoir.v

`within the spirit and 'scope of the following in the plug. By reason ofthisi construction spring normally acting toseat said main means areprovided by which suitable resistvalve. f

3. Ashocl; absorber oomprisinga reservoir, tained to absorb both heavyand light shocks a cylinder having a piston reciproca/brie thereand 'amuch greater flexibility of action is in, means permitting the How ofliquid from attained than in previous instruments of the said reservoir`to said cylinder beneath said type above described. l piston,butpreventing lovy7 in'theop'posite di- It mayv be mentioned that bycausing the rection, a relief port leading from said cylinliquid to passfrom the restricted valve port der to said reservir, a compound valvemech- 41 through the chamber 53 in the plug and anism for said reliefvalve comprising amain thence into the reservoir bubbling or foamvalvefitting-said relief port having itself ing of the liquid in theieservoir isayoided a port of small area adapted to restrict :the vwhich would'ccirif ports were provided How of liquid therethrough, atubular valve in the-wall of the valve stem to discharge the stem onsaid main valvecommunicatin at one end with said -valveport-and'proi'ide at its It will be understood thattheembodiment otherend .With a restricted outlet, a hollow of the invention disclosedherein vis of an valve slidably fitting said valve stem havingillustrative character and is not restrictive a reduced end portion andpresentingsa flat and that various .changes in form, construcface toclose said port and an aperturethrough tion and arrangement of parts maybe made the Wall of said reduced portion communicant claims. lig tvspring tending to seat said auxiliary Having thus described theinvention, what valve, means for restricting the flow' of liquid isclaimed as new, and desired to be secured from said valve stem to saidreservoir and a by Letters Patent, is: relativel heavy spring tendingtoseat said 1. Ashock absorber comprisingareservoir, main va v'e. y f acylinder having a piston reciprocable there- A shoe-lr absorbercomprising a reserin, means permitting the flow of liquid from'viirrcylinder'having a piston reciprocable said reservoir to -saidcylinder beneath ,said tl11`1I1, meI1S pelmlttlllg the ilOW of llquidpiston, but preventing flow in the opposite from 'said reservoir to saldcylinder beneath direction, a relief port leading from said SlldQ1St0I 1,b1 1t prjlventlilg lOW 1n the kOppe- 'cylinder to saidreservoir a compound valve site direction, a reliefport leading fromsaid mechanism forsaid relief port comprising a cylinder tosaidrefscrfVOir, a compound valve main valve littiii said relief videditself --Swit a port o small area main valve fittingsaid relief portlia-vinoF 1tadapted to restrict the fiow of liquid there- Self a Centralport of small area adapted to through, a. hollow auxiliary main valvefor Vrestrict the flow of liquid therethrough, a tusaid valveportprovided with a reduced end bulaiilve Stem 011 Said main Valve(2011111011-v portion having a 1ateral port, communicating nicatig atYone end with said valve seat'and With the chamber of said valve stem, a

port and promechanism for said relief port comprisinc a v with tliechamr of said auxiliary valve and f pI'OVided at its otherend -Witha wallhaving a Springs\ f0r said auxiliary and' main Valves' l'eStIlCtedOutlet Of Substantllly the Same yieldablerespectively to '1i ht andrelatively area as said .valve.port, an auxiliary VlVe heavy pressuresof-theliquld in said cylinder slidably mounted in said tubulin ValveStem, caused by the' `compressive movements of the piston.

2. Ashock absorber comprising a reservoir, close said main valve and achamber enclosa cylinder having apiston reciprocable thereing the end ofsaid valve stemhaving a re in,means pe'ri'nittin"l the iow ofliquid'from stricted communication 4with said reservoir a light springtending to seataid auxiliary valve, a relatively heavy spring tendingtoV said yreservoir to said cylinder beneath said acting to causebuilding up'4 of pressure upon piston, but preventing flow in theopposite dithe endof the valve stem which wi1l supplerection, arelief"port leading from said cylinment the action of the heavy springin correder t0 Saidres'ervqir, a compound valvgmech.- lati on to theincrease 1n the pressure in said anism for said relief .port comprisinga main Cyllndel. valve fitting-said relief .port having `itself a A shckabsorber comprising a reserport of small area adapted to restrict theflow Voir, acyunder having a piston reciproable of liquid therethrough,a tubular valve stern thfr1I1, H 1G&I1S PrlllttmgtllellOW 0f liquidongaid mairfvalve,@Qmmunicatingat on@ end' from 'said reservoir to saidcylinder beneath with said .valveportl and providedat its op-Asaid'pistonrhut preventing lowf inthepppoposite-y end with a restrictedoutlet, a hollow sitedirection, a relief port leading from saidauxiliary valve i slidably mounted in said cylinder 'to said reservoir,aeompound valve valve stem provided with Va reduced end pormechanismforr Suid relief tion havin a lateral port communicating tubularmainvalve s lidab y4 fitting said re-A withthe c amberl vof said hollowauxiliary lief port provided with a lateral outlet and las portcomprising a a central port of small area and having a tagpered outerWall, a tubular valve stem on said :face to engage said tapered valveseat, and

having an aperture in the Wall of said reduced end portion communicatingWith the chamber of said auxiliary valve t0 permit the liquid, upon theopening of the valve, to flow through its chamber into the valve stem, alight spring tendiner to seat said auxiliary valve anda relatively heavyspring tending to seat said main valve.

6. A'shock absorber comprising a reservoir, a cylinder having a pistonreciprocable therein, means permitting the flow ofliquid from saidreservoir to said cylinder beneath said pistonfbut preventing flow inthe opposite direction, a relief port leading from saidl cylinder tosaid reservoir, a compound valve mechanism for said relief portcomprising a tubular main valve slidably fitting said relief portprovided with a lateral outlet and with a central port of small area andhaving a tub/ular valve stem provided with a restricted port at adistance from said valve, a screen Within said tubular valve seat ofgreater area than said valve port acting to prevent clogging of saidvalve port, an auxiliary valve for saidl valve port and light and heavylsprings tending respectively to seatsaid auxiliary and main valves. f

7. A, shock absorber comprising a casing having an interior Walldividing the chamber thereof into a reservoir and a cylinder, a tulbular piston reciprocable in said cylinder having in its head a port, aspring actuated inlet valve acting to permit free iow ofliquid from thereservoir into the cylinder and an aperture in the skirt of said piston,a relief port communicating with said cylinder through said aperturesubstantially midway of the length ofthe cylinder and a compound valvemechanism for said relief port including an auxiliary and a main valveyieldable respectively to light and relatively heavy ressures of thelliquid in said cylinder caused by the compressive movements of thepiston. In testimony whereof, I have signed my name to thisspecification,

RALPH M. LovEJoY.

